fix(ray_trace): don't treat zero yaw/pitch as missing in blockAtEntityCursor

[AnonymoDGH]

Fixes #3935

Problem

bot.blockAtEntityCursor() validated the entity orientation with truthiness checks:

if (!entity.position || !entity.height || !entity.pitch || !entity.yaw) return null

Because 0 is falsy in JavaScript, a perfectly valid orientation with yaw === 0 or pitch === 0 (facing due south / looking level) was treated as if the value were missing, and the ray trace was skipped — the function returned null even though the entity was correctly oriented.

Fix

Validate with Number.isFinite instead of truthiness, so only genuinely missing (null/undefined) or non-finite (NaN/Infinity) values are rejected, while 0 is accepted:

if (!entity.position) return null
const { position, height, pitch, yaw } = entity
if (!Number.isFinite(height) || !Number.isFinite(pitch) || !Number.isFinite(yaw)) return null

This is equivalent to the issue's proposed two-part isMissing || isInvalid check but in a single condition, and it keeps the existing behavior for all invalid inputs.

Verified

• Standalone check of the new validation across 11 cases: yaw=0, pitch=0, yaw=0 && pitch=0, normal values, and height=0 all proceed to the ray trace; missing height/pitch/yaw, NaN, Infinity, and missing position all return null.
• Added a regression test to test/externalTests/rayTrace.js (which runs in CI): it builds a small stone wall ahead at eye level, sets yaw = 0 and pitch = 0, and asserts blockAtEntityCursor finds the wall instead of returning null.
• standard lint passes on both changed files.